Abstract
In most countries, sanitary landfill is nowadays the most common way to eliminate municipal solid wastes (MSWs). However, sanitary landfill generates large quantity of heavily polluted leachate, which can induce ecological risk and potential hazards towards public health and ecosystems. The application of advanced oxidation processes (AOPs) including ozone-based oxidation, Fenton oxidation, electrochemical oxidation, and other AOPs to treatment of landfill leachate was reviewed. The treatment efficiency in term of chemical oxygen demand (COD) of various AOPs was presented. Advantages and drawbacks of various AOPs were discussed. Among the AOPs reviewed, Fenton process should be the best choice, not only because it can achieve about 49~89% of COD removal with COD ranging from 837 to 8894 mg/L, but also because the process is cost-effective and simple in technological aspect, there is no mass transfer limitation (homogeneous nature) and both iron and hydrogen peroxide are nontoxic.
Highlights
Due to rapid economic development in recent years, the excessive generation of municipal solid wastes (MSWs) has been identified as one of the most serious environmental problems in the world which needs to be addressed urgently for environmental protection
The young landfill leachate is commonly characterized by high biochemical oxygen demand (BOD) (4000–13,000 mg/L) and chemical oxygen demand (COD) (30,000–60,000 mg/L), moderately high content of ammonium nitrogen (500–2000 mg/L), high ratio of BOD/COD, and low pH values, with biodegradable volatile fatty acids (VFAs) appear to be its major constituents [5]
Based on the analysis and Lopez et al [49], Fenton process seems to be the best compromise because the process is technologically simple, there is no mass transfer limitation and both iron and hydrogen peroxide are relatively cheap and nontoxic
Summary
Due to rapid economic development in recent years, the excessive generation of municipal solid wastes (MSWs) has been identified as one of the most serious environmental problems in the world which needs to be addressed urgently for environmental protection. Biological treatment processes, including anaerobic and aerobic processes, are quite effective for leachate generated in the early stage with a high BOD5/COD They generally fail to treat a leachate with a rather low BOD5/COD, or high concentration of toxic metals [11]. Among the various types of physical-chemical treatments, advanced oxidation processes (AOPs) has been reported as one of the most effective method to degrade a variety of refractory compounds in landfill leachate [12]. This can be attributed to the role of a highly reactive radical intermediate such as hydroxyl radical (OH) as an oxidant. The kinetic rate of AOPs depends on the concentration of radicals and pollutants, temperature as well as the presence of scavengers such as bicarbonate ion [14]
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